'Ruby' Issues

RDV · February 09, 2004, 01:37:48 PM

I converted my Little Gem to Ruby specs, but it's strange, when I added the 10ka input pot I no longer had any real control over the gain, in fact I just put a jumper between pins 1 & 8 which make it sound like it did before with the pins open. Any resistance between 1 & 8 and you've got nothing. I know the first thing everyone thinks is 'he's made a wiring mistake' which is understandable, but all I did was insert the pot between the input cap and pin 2 of the JRC386, remove the RC filter, and put a .1uF from pin 7 to ground. I already had a J-Fet input buffer. What gives? I like it like this though, cause I like it to be clean & use pedals for breakup, but I want to know why the change in character.

Regards

RDV

B Tremblay · February 09, 2004, 01:57:44 PM

That's an odd problem.

Does the volume control function correctly? If not, describe its operation.

What is your battery voltage? As you may know, the 3386 can behave erratically when the power is low.

Is it possible you damaged the IC while soldering?

Does the Gain pot work at all?

RDV · February 09, 2004, 03:59:11 PM

Quote from: B TremblayThat's an odd problem.
1. Does the volume control function correctly? If not, describe its operation.
2. What is your battery voltage? As you may know, the 386 can behave erratically when the power is low.
3. Is it possible you damaged the IC while soldering?
4. Does the Gain pot work at all?

1. Yes, it's great for playing down low.
2. 14v wall wart(unregulated 9v)
3. Socketed
4. I removed it as I was going to just have it with the pins open for low gain operation cause I had been leaving it down all the time anyway, but with the pins open I hardly had any sound at all, so I actually had to jumper them to get it to the previous pins open level .

I plan on messing with it some more when I get home from work. I may build a new one from scratch and see how that works. It sounds really good though, clear & distortion free.

Regards

RDV

smoguzbenjamin · February 09, 2004, 04:29:36 PM

I had this problem with an LM386n-1 that my guitar signal was too hot, and it started clipping. I added a threshold (pre-volume) pot in to compensate but It shouldn't be doing that in the first place shouldn't it? Or have I bought some crappy ICs?

javacody · February 09, 2004, 11:19:59 PM

I had no problems with the Ruby other than the j201 doesn't like more than 9volts in this configuration. I followed the schems and the layout and had no issues (other than a burned out j201).

Did you ground pin 3?

I noticed with my first attempt that I missed grounding the 0.1 uF cap and there seemed to be little volume.

smoguzbenjamin · February 10, 2004, 12:10:24 PM

I followed all the procedures to stop it oscillating and make it sound good. Maybe the guy just gave me a bad chip... :?

RDV · February 10, 2004, 12:17:39 PM

Quote from: javacodyDid you ground pin 3?

Yes.

Regards

RDV

B Tremblay · February 10, 2004, 02:21:07 PM

I got my parts order today and tried MPF102 and 2N5457 in the buffer of Ruby. Both added a bit of volume and shine to the sound. They each worked well with a 9v battery and 12v (actually 11.25v) from an 8 AA pack with no modifications.

Of the three FETs, I prefer the MPF102 in Ruby.

javacody · February 10, 2004, 06:54:02 PM

Well, what the heck am I doing wrong? I tried a j201 at 12volts and it sounded misbiased. I also tried a 2n5457 and it got so hot that it burned my fingers. I tried an MPF102 and it just squealed? Any ideas what I did wrong?

RDV · February 10, 2004, 07:24:45 PM

Quote from: javacodyWell, what the heck am I doing wrong? I tried a j201 at 12volts and it sounded misbiased. I also tried a 2n5457 and it got so hot that it burned my fingers. I tried an MPF102 and it just squealed? Any ideas what I did wrong?

JFet pinouts will get you, they never make sense like a good ol' BJT.

Regards

RDV

javacody · February 10, 2004, 07:39:49 PM

Actually, my issue was a hair sized solder bridge between the ground and the source. The J201 worked fine with this, but the MPF102 and 2n5457 couldn't take it. Funny, huh? Anyway, issue solved. The MPF102 does indeed sound best.

B Tremblay · February 10, 2004, 08:17:15 PM

I'm glad to hear that you tracked down the problem!

javacody · February 10, 2004, 09:06:57 PM

Its funny isn't it, how people assume there is something wrong with the design, when 99% of the time, its a mistake they made?

RDV · February 10, 2004, 11:04:45 PM

Tonight I ditched the old board I had my 'Gem' on(it had been modded one too many times) and built a nice new 'Ruby' to the exact specs and everything. It is nice, but with the volume control I don't quite see the usefulness of the gain knob. With it(gain) all the way up you can still bring it down to a whisper with the volume knob. I think I'll wire pins 1 & 8 together and use the hole I drilled(for the gain knob) for an LED or something.

Regards

RDV

BILLYL · February 11, 2004, 08:00:51 AM

Just finished up the RUBY and thanks for these posts. One question I had - since I really don't know that much about IC's - if I wanted to add a TONE control how would I do that?

Thanks

BILLYL

PS - any recommendations about learning about IC?

RDV · February 11, 2004, 08:33:04 AM

Quote from: BILLYL...if I wanted to add a TONE control how would I do that?

I would do an input cap blend using the stock cap value(.047uF) as one cap and a .0068uF or maybe a .001uF as the other. If you do a 'cap to ground' style tone control you'll lose some volume IMHO.

Just my 2 cents

RDV

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'Ruby' Issues